U.S. patent number 4,936,840 [Application Number 07/140,000] was granted by the patent office on 1990-06-26 for method of reducing fastener irritation and waist droop in a disposable diaper.
This patent grant is currently assigned to Kimberly-Clark Corporation. Invention is credited to Deborah L. Proxmire.
United States Patent |
4,936,840 |
Proxmire |
June 26, 1990 |
Method of reducing fastener irritation and waist droop in a
disposable diaper
Abstract
A method is disclosed for making a fastener landing zone within
a selected area on the front waist panel of a diaper. The front
waist panel and a rear waist panel are stretchable in a cross-body
direction, the rear panel having elongated ears bearing mechanical
fasteners on inner, body-facing surfaces thereof which are
releasably engageable with mechanical fasteners provided on the
landing zones. The landing zones are shaped, sized and oriented on
the front waist panel so as to impart a tensile force distribution
pattern thereacross, directing tensile stresses away from the leg
and waist openings while providing a band of abdominal support
across the front waist panel between the landing zones.
Inventors: |
Proxmire; Deborah L. (Larsen,
WI) |
Assignee: |
Kimberly-Clark Corporation
(Neenah, WI)
|
Family
ID: |
22489275 |
Appl.
No.: |
07/140,000 |
Filed: |
December 31, 1987 |
Current U.S.
Class: |
604/385.22;
604/391; 604/397 |
Current CPC
Class: |
A61F
13/49011 (20130101); A61F 13/49453 (20130101); A61F
13/505 (20130101); A61F 13/5633 (20130101); A61F
13/627 (20130101); A61F 2013/49033 (20130101); A61F
2013/49042 (20130101); A61F 2013/5694 (20130101) |
Current International
Class: |
A61F
13/56 (20060101); A61F 13/62 (20060101); A61F
13/15 (20060101); A61F 013/16 () |
Field of
Search: |
;604/385.1,385.2,386,387,389,390,391,392,393,394,395,396,397,398,399,400,401,402 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Green; Randall L.
Assistant Examiner: Reichle; K. M.
Attorney, Agent or Firm: Miller; Douglas L.
Claims
We claim:
1. A method of making a fixed fastener landing zone on an
elastomeric surface of a garment, said method comprising the steps
of:
(a) providing an elastomeric nonwoven outer cover adapted for
selected bodily registration;
(b) providing said outer cover with front and rear waist panels
resiliently stretchable in a direction essentially transverse to a
longitudinal axis of said outer cover;
(c) providing said outer cover with an intermediate crotch panel
separating said waist panels from one another, with a pair of sides
extending between and interconnecting said waist panels, delimiting
a pair of elastically contractible leg openings along said sides of
said crotch panel and delimiting a front and a rear longitudinally
opposed pair of ears separated from one another by said crotch
panel and comprising outermost lateral portions of said front and
rear waist panels, respectively, wherein corresponding ones of said
front and rear pairs of ears are engageable with one another to
define an elastically contractible waist opening;
(d) providing said rear pair of ears with elongated shapes
presenting first surfaces superposable on second surfaces of said
front pair of ears;
(e) providing first fastening means on said first surfaces of said
rear pair of ears;
(f) forming inelastic landing zones on said second surfaces of said
front ears and providing second fastening means on said landing
zones that are releasably engageable with said first fastening
means on said first surfaces of said rear ears, said inelastic
landing zones tapering in dimension, in a decreasing manner,
towards the longitudinal axis of said outer cover, whereby the
formed inelastic landing zones selectively restrict the
stretchability of said second surfaces and provide a tensile force
distribution pattern across said front waist panel which directs
tensile stresses away from said leg and waist openings while
providing a band of abdominal support across said front waist panel
between said landing zones when said outer cover is securely
worn.
2. The method of claim 1 further comprising the steps of shaping
said landing zones in generally triangular configurations and
orienting said landing zones with respect to one another so that an
area of highest tension is created in said band of abdominal
support along a minimum distance between respective apexes of said
landing zones that are equidistantly spaced on opposed sides of
longitudinal axis.
3. The method of claim 1 further comprising the step of providing
respective mechanical fastening means on said first and said second
surfaces.
4. The method of claim 3 wherein said first and said second
fastening means are hook and loop fasteners.
5. The method of claim 1 further comprising the step of forming a
pattern of autogenous bonds surrounding said landing zones.
6. The method of claim 5 wherein the step of forming is by
ultrasonically forming the pattern of bonds.
7. The method of claim 1 wherein the step of providing an
elastomeric nonwoven outer cover further includes providing an
elastomeric nonwoven outer cover that is resiliently stretchable
from about 20 percent to about 200 percent.
8. The method of claim 1 wherein the step of providing an
elastomeric nonwoven outer cover further includes providing an
elastomeric nonwoven outer cover that is breathable.
9. The method of claim 1 wherein the step of providing an
elastomeric nonwoven outer cover further includes forming said
outer cover as a stretchbonded laminate by joining an elastic layer
to at least one gatherable layer.
Description
TECHNICAL FIELD
The present invention relates, generally, to the field of
disposable garments utilized for the absorption and containment of
urine and other bodily exudates. More particularly, the present
invention relates to disposable infant and adult diapers.
BACKGROUND OF THE INVENTION
This application is an improvement over U.S. Pat. No. 4,701,175,
assigned to the assignee of the instant application. Disposable
garments are generally well known in the art and have become an
important and an essentially indispensable sanitary protection
item, most particularly in the field of infant and child care where
disposable diapers provide for the absorption and containment of
urine and other bodily exudates. Present commercially available
disposable diapers are generally unitary, preshaped and prefolded,
and comprised of a porous facing layer and a fluid impervious
backing sheet with an absorbent material disposed therebetween.
These presently available disposable diapers have met a particular
need and have become ever increasingly popular. However, even
though the present available disposable diapers have achieved a
certain degree of efficiency and effectiveness, several draw-backs
remain that have been identified by mothers of infants wearing the
diapers. These mothers have strongly voiced their desire to be able
to obtain disposable diapers that are aesthetically neat and
attractive when on their infant or child. The aesthetically neat
criteria have been identified as including a trim, slim fit, and a
neat fitting waist and legs that do not allow leakage of urine or
feces. It has also been found that mothers do not want their
children looking rumpled, bulky or messy. In addition, these
mothers have expressed the desire to either have a disposable
diaper that fits more sizes of babies or to have disposable diapers
provided in more sizes.
The typical disposable diaper has a three-layer composite structure
comprising a liquid permeable bodyside inner liner, a liquid
impermeable outer cover and an absorbent batt sandwiched between
the liner and the cover. Materials now in general use for the three
principal elements of a disposable diaper include various types of
nonwoven fabrics for the bodyside liner, a thin thermoplastic film
for the outer cover and cellulosic fluff for the absorbent batt.
Examples of present disposable diapers are taught in U.S. Pat. No.
4,324,245 to Mesek, et al., U.S. Pat. No. 3,196,874 to Hrubecky,
and U.S. Pat. No. 4,050,462 to Woon, et al.
Other prior art diaper constructions, disclosed in the references
listed below, have sought to provide waste containment with a
reusable diaper holder receiving an absorbent structure,
to-wit:
1. U.S. Pat. No. 3,658,064 to Pociluyko and U.S. Pat. No. 3,370,590
to Hokanson, et al.;
2. U.S. Pat. No. 4,425,128 to Motomura;
3. U.S. Pat. No. 2,141,105 to Eller;
4. U.S. Pat. No. 4,397,646 to Daniels, et al.;
5. U.S. Pat. Nos. 4,597,761, 4,496,360 and 4,597,760.
U.S. Pat. No. 4,166,464 to Korpman, discloses an elastic fluid
impermeable backing film laminated to an absorbent layer to
ostensibly provide enhanced conformability to the body surface.
U.S. Pat. Nos. 4,355,425 to Jones, et al. and 3,644,157 to Draper
disclose disposable stretchable nonwoven panties containing small
crotch pads unsuitable for absorbing and containing body
wastes.
Even where prior art designs have attempted to use impermeable
elastic film barriers, there has been inadequate recognition of the
functional problems associated with an elastic outer cover.
Further, costly woven diaper holders or overpants, designed to be
waterproof and reusable, do not offer disposability.
U.S. Pat. No. 4,586,199 to Birring discloses an elastic brief for
use with a conventional disposable diaper. The brief is provided
with front and rear crocheted elastic pieces which exert increased
pressure along the sides of the underlying diaper to ostensibly
hold it in place and seal the edges of the diaper against the body.
The crocheting of the brief, to which the diaper is not physically
attached, is looser in a central area in the front and back pieces
to concentrate greater tension along the sides of the diaper at the
legs and waist. This increased stress along the sides can lead to
undesirable pinching by the garment at the legs and waist openings,
leaving red marks and abrasions on the skin.
British patent application No. 2,185,383, published July 22,
1987discloses an integral unitary disposable diaper having
elasticized leg openings and fastening tapes with a tapered user's
end, ostensibly for wearer comfort and easier handling during
application thereof. The use of an elastomeric outer diaper cover
is not disclosed in this document.
U.S. Pat. No. 4,701,175, assigned to the instant assignee,
discloses a form-fitting, self-adjusting disposable garment
comprising an elastomeric nonwoven outer cover having an absorbent
insert structure attached and integrated thereinto.
Although the above-mentioned prior art garments are provided with
elasticized leg and/or waist openings, there is still a tendency
for the garment to blouse outwardly from the body at the hip and
abdominal regions and to sag downwardly in the abdominal region.
There is also a further tendency for tensile stresses to
concentrate undesirably along the leg and waist openings of the
garment. Thus, there remains a need for an anatomically
form-fitting, generally self-adjusting disposable garment which
provides additional support to keep the garment from sagging at the
waist and drooping at the lower abdomen.
SUMMARY OF THE INVENTION AND ADVANTAGES
According to the invention, there is disclosed a method of making a
fixed fastener landing zone on an appointed elastomeric surface of
a waste-containment garment. The method comprises the steps of
providing absorbent means adapted for absorbing and containing body
wastes and providing an elastomeric nonwoven outer cover adapted
for holding the absorbent means in a selected bodily registration
when the garment is securely worn. The outer cover is provided with
front and rear waist panels resiliently stretchable in a cross-body
direction essentially transverse to a line centered on the
longitudinal axis of said garment. An intermediate crotch panel
separates the waist panels from one another and a pair of sides
extend between and interconnect the waist panels, delimiting a pair
of elastically contractible or expansible leg openings along the
sides of the crotch panel and delimiting front and rear
longitudinally opposed pairs of ears separated from one another by
the crotch panel and comprising outermost lateral portions of the
front and rear waist panels, respectively. Corresponding ones of
the front and rear pairs of ears are engageable with one another to
define an elastically contractible or expansible waist opening and
the ears are provided with elongated shapes presenting inner,
body-facing surfaces superposable on externally-facing surfaces of
the front pair of ears. Fastening means are provided on the inner
surfaces of the rear pair of ears and inelastic landing zones are
appointed on given areas of the external surfaces, fastening means
being provided on the landing zones to present cooperating
fastening means releasably engageable with those provided on the
rear ears. The landing zones are selectively shaped, sized and then
oriented on the external surfaces, restricting the stretchability
thereof within the given areas and thereby imparting a tensile
force distribution pattern across the front waist panel which
directs tensile stresses away from the leg and waist openings while
providing a band of abdominal support across the front waist panel
between the landing zones when the garment is securely worn.
In a preferred embodiment of the invention, the landing zones are
truncated inwardly toward the centerline and have hook and loop
mechanical fastening tapes provided thereon.
In a further preferred embodiment, the shape and orientation of the
landing zones is selected to direct tensile stresses away from the
leg and waist openings along the abdominal band of support.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the disclosed invention can be seen in
the following drawings:
FIG. 1 is a schematic view indicating the lines of support of the
present invention relative to the body;
FIG. 2 is an internal perspective view of the invention shown prior
to wear;
FIG. 3 is a sectional view of cross-section 3--3 of Figure 2;
FIG. 4 is a side view of the disposable absorbent garment of the
present invention shown secured around a baby;
FIG. 5 is a front view of the disposable absorbent garment of the
present invention shown secured around a baby;
FIG. 6 is a back view of the disposable absorbent garment of the
present invention shown secured around a baby;
FIG. 7 is a front view of the disposable absorbent garment of the
present invention showing the disposition of the garment on the
wearer after being worn for a period of time;
FIG. 8 is a perspective view of the garment of the present
invention, showing fastener landing zones of the present
invention;
FIG. 8A is a partial perspective view of a fastener landing zone
constructed in accordance with the present invention;
FIG. 9A is a sequential view showing an alternative fastening
system constructed in accordance with the present invention;
FIG. 9B is a sequential view of FIG. 9A;
FIG. 10 is an internal perspective view of the garment of the
present invention;
FIG. 10A is a sectional view of cross--section 10A--10A of FIG.
10;
FIG. 11 is an exploded perspective view of the garment of the
present invention;
FIG. 12A is a schematic view of the front waist panel of the
present invention;
FIG. 12B is a schematic view of the front waist panel of the
present invention;
FIG. 12C is a schematic view of the front waist panel of the
present invention;
FIG. 13 is a side view of a disposable absorbent garment shown
secured about a wearer by the fastening system of the present
invention;
FIG. 14 is a front view of a disposable absorbent garment shown
secured about a wearer by the fastening system of the present
invention;
FIG. 15 is a back view of a disposable absorbent garment shown
secured about a wearer by the fastening system of the present
invention; and
FIG. 16 is a front view of a disposable absorbent garment secured
about a wearer by the fastening system of the present invention,
showing the disposition of the garment on a wearer after being worn
for a period of time.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the figures, there are shown one or more preferred
embodiments to the present invention as would be used in a
disposable diaper. As used herein, the term disposable diaper
refers to articles which absorb and contain liquid, and more
specifically, refers to absorbent articles which are placed against
or in proximity to the human body to absorb and contain the various
solid or liquid wastes discharged therefrom, for example, urine and
feces and, further, which articles are intended to be discarded
after a single use (that is, they are not intended to be laundered
or otherwise restored and reused). A "diaper" is a garment
generally worn by infants or incontinent persons, which is drawn up
between the legs and fastened about the waist of the user. It
should be understood, however, that the present invention is also
applicable for use in other disposable absorbent articles used as
training pants and the like.
Referring to FIG. 2, according to the instant invention, there is
provided an anatomically form-fitting, generally self-adjusting
disposable absorbent garment, generally shown at 10, such as a
disposable diaper, comprising an elastomeric outer cover, generally
indicated at 12, including opposed front 13 and rear 14 waist
sections together defining a waist opening and a pair of sides
generally shown at 15 extending between and interconnecting the
waist sections. A crotch section, generally indicated at 16, is
situated between a pair of leg openings 18 delimited along said
sides 15 at outermost portions of said crotch section 16. Ear
portions 20, 22, 24, 26 are also delimited along the sides 15
generally between the opposed waist sections 13, 14 and each of the
leg openings 18, respectively, with longitudinally opposed pairs
20, 24 and 22, 26 of said ears being engageable with one another
about the body of a wearer. The outer cover 12 preferably has a
generally hourglass or T-shaped configuration, with the leg
openings 18 cut-out from the sides 15 thereof, defining a front
waist panel 28 having a laterally opposed front pair of ear
portions 24, 26 in conjunction therewith and a rear waist panel 30
having another laterally opposed rear pair of the ear portions 20,
22 in conjunction therewith. The front 28 and rear 30 waist panels
are separated from one another by the crotch section 16, which is
narrowed due to the converging leg cut-out openings 18 and extend
between the laterally opposed front and rear pairs of ears,
respectively, between the corresponding waist sections and the leg
openings as shown in the figures.
With continuing reference to FIG. 2, and also to FIG. 3, there is
depicted an absorbent insert structure, generally indicated at 32,
substantially superposable on the front 28 and rear 30 panels and
the crotch section 16 of the outer cover 12 for absorbing and
containing bodily exudates, particularly urine and feces. The
absorbent structure 32 includes: a liquid permeable bodyside liner
34, for example, a commercially available pattern-bonded,
spunbonded polypropylene web that may have a basis weight of from
about 0.2 to 0.8 oz./yd.sup.2.; a liquid impermeable barrier 36,
for example, a commercially available plastic film of polypropylene
or the like; and an absorbent core 38 disposed therebetween. As
shown in FIG. 11, the absorbent structure 32 is in the form of a
separate insert, typically of materials which are substantially
nonstretchable, attached and integrated into the resiliently
stretchable outer cover 12, preferably using autogenous bonds of
the type generated thermally or ultrasonically, while allowing
substantially unrestricted functional stretchability of the outer
cover in a manner hereinafter described. A preferably continuous
ultrasonic or thermal perimeter bond 40 sealingly secures the
absorbent structure 32 together to prevent leakage therefrom by
bonding the liner 34 and barrier 36 peripherally to one another,
making the liner and barrier coterminous with one another, about
the absorbent core 38 disposed therebetween. It is important that
the materials of the barrier 36 and liner 34 be compatible with one
another and with the material of the outer cover 12 for autogenous
bonding. Accordingly, polypropylene and other polyolefins or
polyolefin blends have been found to be suitable and economical
polymeric materials for use in the liner, barrier and outer cover
of the instant garment 10.
The outer cover 12 generally comprises an air-permeable, i.e.,
"breathable", elastomeric nonwoven material, particularly a
stretch-bonded laminar fabric wherein an elastic nonwoven web is
joined to one or more gatherable nonwoven webs of the type
described in greater detail herein. Preferably, the nonwoven
laminate is resiliently stretchable from about 20 to about 200
percent in an essentially cross-body direction 41 which is
transverse to a longitudinal axis of the garment.
The longitudinally opposed ears 20, 24, 22, 26, which are
engageable about a wearer, are releasably fastenable with one
another, forming full-length closures extending substantially from
the waist to the leg openings of the outer cover. The full-length
closures further provide dimensional integrity to the resiliently
stretchable garment during various and even extreme bodily
movements and positions of the wearer. Since the garment is
form-fitting and self-adjusting, it does not gap or collapse at the
hip and waist regions. The various fastening systems used in the
invention are also detailed herein.
Preferably, the waist sections 13, 14 of the outer cover 12 have
the insert 32 attached and integrated thereinto by attachment means
according to the present invention as will be set forth more fully
below.
With respect to the attachment means of the present invention as
shown in FIGS. 2 and 3, it is important to minimize the number of
bonds and total bond area used in integrating the relatively
unstretchable absorbent insert to the stretchable outer cover or,
where forming hems, the number of bonds used to bond the outer
cover to itself. The Applicants have discovered that the number of
bonds correspondingly affects the stretch elongation in the
elastomeric component that is bonded. Not only does a lesser number
of bonds result in less stretch loss, but the greater the spacing
apart of bond points, the less stretch elongation is affected.
Accordingly, bonding patterns should be selected that significantly
reduce the amount of stretch lost by means of the density and
spacing of the bond points. Specifically, the lower the number and
density of the bonds 44 for attaching and integrating the insert 32
along the waist sections 13, 14, the less stretch is inhibited in
said waist sections. For example, if the waist section is
stretchable in a cross-body direction and the insert is attached
thereto at two points lying on a line extending also in said
cross-body direction, then the stretchability of the outer cover
waist section along that line is restricted between those two
points of attachment by the least stretchable element present
between those points, such as the liner and barrier of the insert
or, further, the absorbent core which may be glued to the barrier
with, e.g., hot melt construction adhesive. Similarly, the insert
may also be attached and integrated at the crotch section.
Therefore, the garment of the present invention includes attachment
means for attaching and integrating the absorbent insert structure
32, which is generally inelastic, into the relatively resiliently
stretchable elastomeric outer cover which is used for positioning
the insert in a selected bodily registration, while allowing
substantially unrestricted functional stretchability thereof. Thus,
the total garment is maintained anatomically form-fitting and
generally self-adjusting.
These and other objectives have heretofore been addressed by
Applicant's prior copending application Ser. No. 947,947, filed
Dec. 31, 1986, now U.S. Pat. No. 4,770,656, the entire disclosure
of which is expressely incorporated by reference herein and relied
upon. Referring to FIGS. 2 and 4-7, full-length closures of the
type disclosed in this referenced application may have cooperating
primary closures, e.g., snaps, adjacent the waist and leg openings
of each full-length closure, and cooperating secondary closures,
e.g., hook and loop tapes, extending between each of the
cooperating pairs of primary closures.
The instant garment 10 is generally constructed and assembled as
shown in FIG. 2 and, with respect to other alternative embodiments,
in FIGS. 10 and 11. The bonds 44 attach and integrate the opposed
longitudinal ends 48, 50 of the absorbent insert 32 to said outer
cover 12 at selected front 52 and rear 54 waist attachment zones
along said front 13 and rear 14 waist sections, respectively,
defining one or more free-span zones 56 underlying said insert 32
wherein the functional stretchability of said outer cover in said
free-span zone 56 is substantially unrestricted. It will be
understood that where the insert 32 is integrated only at the waist
attachment zones 52, 54, i.e., not at the crotch section 16, the
free-span zone wherein the outer cover stretchability is
substantially unrestricted underlies the entire longitudinal span
of the absorbent insert 32. Significantly, the free-span zone 56
also includes those portions of the waist sections 13, 14 not
included in the waist attachment zones 52, 54. It will also be
understood that the insert 32 may be adequately held by the outer
cover 12 in registration with the body of the wearer without
significant sideways shifting. Additional bonding of the insert in
the free-span zone 56 to the front 28 or rear 30 panels or the
crotch section 16 is not required.
Although the free-span zones 56 can be provided in either of the
front 28 and rear 30 panels, it is important that the rear panel 30
have substantially unrestricted stretch properties from waist to
leg across the lateral span of the rear panel 30 from one of the
rear pair of ears 24 to the other ear 26. Cross-body direction
stretch of the crotch section 16 of the outer cover 12 during use
is minimally required so that bonding of the insert 32 at or near
the leg openings 18 of the crotch section 16 does not significantly
affect the overall cross-body stretch properties of the outer
cover, that is, the ability to be resiliently stretchable across
the area defined by the front 28 or rear 30 waist panels.
The breathable outer cover 12 which, among other functions, holds
the insert 32 in proper bodily registration, is not itself required
to provide a liquid waste-containment barrier, unlike the prior
art. In fact, application Ser. No. 947,942 also teaches a garment
having a disposable insert which may be removed and replaced using
snaps or the like, so that the outer cover becomes reusable, in
this regard, the garment of the instant invention could also have a
reusable outer cover and disposable insert system.
Referring again to FIG. 11, the absorbent insert 32 may further
comprise at least one but preferably a pair of front 62 and rear 64
waist attachment flaps respectively situated at the opposed
longitudinal ends 48, 50 of the insert 32. The flaps 62, 64 extend
longitudinally from and contiguous with the liner 34 beyond the
terminal ends of the absorbent composite 38, the flaps being bonded
or otherwise attached to said front 13 and rear 14 waist sections,
respectively, in said waist attachment zones 52, 54. The front 13
and rear 14 waist sections preferably have finished waist hems 66
along the waist opening wherein the waist attachment flaps 62, 64
are entrapped and bonded. The waist hems 66 comprise inwardly
folded-over edges of said waist sections 13, 14. The waist
attachment flaps 62, 64 (FIG. 11) may comprise coextensions of the
barrier 36 and liner 34 or may comprise extensions of either the
barrier 36 or liner 34 alone. Although the flaps 62, 64 typically
comprise a nonwoven liner and plastic film materials that are not
inherently stretchable relative to the outer cover 12, the flaps
62, 64 themselves need not be contiguous with the liner or barrier
material.
Referring to FIGS. 2, 4, 5 and 7, according to the instant
invention, there is provided an abdominal support band 65 attached
to the front waist panel 28 and extending in the essentially
cross-body direction indicated by arrow 41 across at least the
central portion of the front waist panel 28. The abdominal support
band 65 has a modulus of elasticity which is selected to either be
greater or less than the modulus of elasticity of the front waist
panel 28 in the essentially cross-body direction 41, depending on
the desired fit characteristics of the garment 10. Where
contractability of the garment 10 is employed in order to achieve
the desired fit for a range of body sizes, the outer cover 12 will
be sized to fit larger body sizes within the given range and then
supplemental elasticization in the waist and legs is provided to
shorten the garment openings to fit the torso and thighs of a
particular wearer. In this case, the supplemental elastics, such as
the leg elastics 58 and the abdominal support band 65, must have a
modulus of elasticity selected to provide a greater tension than
the remaining portions of the outer cover to which the elastics 58,
65 are not attached. Conversely, where expansibility of the garment
is employed to achieve the desired fit characteristics of the outer
cover, the outer cover 12 is sized to fit smaller sized individuals
within the given range of sizes, utilizing the inherent
stretchability of the outer cover material to expand and
accommodate the dimensions of the torso and legs of a particular
wearer. The abdominal support band 65 may be an extruded
elastomeric film or nonwoven material which, in the case where the
band 65 has a greater tension than the remainder of the front
panel, be attached to the front panel in a stretched condition
with, for example, adhesive, or, in the case where the support band
65 has a lower modulus of elasticity than the remainder of the
front panel 28, the support band may comprise a band of the outer
cover which has been bonded, either autogenously by thermal or
ultrasonic means, or adhesively by attaching an adhesive piece to
the front waist panel 28, thereby negating the stretch properties
of the band which is thus bonded.
Referring to FIG. 1, the waist opening W defined by the front 13
and back 14 waist sections of the diaper is the desired positioning
for proper fit of the garment of the present invention. The natural
support line for the diaper, designated by the letter S, runs from
the small of the back, over the hip and on the lower side of the
protruding stomach. The distance from the small of the back up to
the waist is represented by the designation d.sub.1 and d.sub.2
represents the distance from the support line S to the waist
opening W. The distance d.sub.2 is longer than the distance d.sub.1
by about 1 to 3 inches. By providing disposable diapers with a
support band located about 1 to 3 inches below the waistband, the
diaper will be held in position better with less front panel drop
than is seen in currently available commercial diapers. The panels
28, 30 will be held up from below the support band. The support
band can take a number of forms. First, in a conventional unitary
disposable diaper, the band could be an elastomeric material
stretched then attached to the outer cover so as to contract the
plastic film outer cover and provide a contractible force along the
support lines (not shown).
The band 65 can be located in the front waist panel only, the rear
panel 30 as well or a portion only of the front and back. Elastic
waistbands currently provided in disposable diapers do not serve
the function of the instant support band 65 since they provide
mainly an aesthetic nonsupporting waist line appearance, e.g.,
along the line W.
Referring again to FIG. 2, additional elastication or bonding
between other areas of the outer cover 12 and absorbent insert 32
may be provided. Specifically, supplemental leg elastics 58 may be
applied to outermost portions of the crotch section 16 around the
inner curvature of the leg openings 18 to gather the garment 10
about the thighs of the wearer. Crotch elastics 60 may be applied
to the liner 34 to cause the insert to more closely conform to the
contours of the wearer's perineal region.
The leg elastics 58 preferably comprise a breathable elastomeric
nonwoven laminate of the type described in said prior copending
U.S. Pat. application Ser. No. 947,947 of applicant. The leg
elastic members 58 function cooperably with the stretchable outer
cover for gathering the leg openings 18 about the wearer and can be
applied in varying tensions relative thereto by adhesive,
autogenous or pressure bonding. Leg hems (not shown) may
alternatively be formed at the curved leg openings 18 in addition
to the waist sections 13, 14, resulting in increased tension due to
the increased thickness of the elastomeric material of the outer
cover at the folded over hem. For this purpose, additional
elasticized gathers (not shown) of, e.g., FULLASTIC.RTM., a
trademarked extruded elastomeric film material sold by H. B. Fuller
Company of Minneapolis, Minn., can be entrapped within the waist
hems 66 and any leg hems (not shown) to provide such additional
elastic gathering. Although the waist opening has heretofore been
discussed in conjunction with waist hems 66 and optional waist
elastics entrapped therein, a nonwoven elastomeric laminar material
of the type described for the leg elastics 58 could be applied as a
border strip (not shown) along the waist sections 13, 14 defining
the waist opening.
As can be seen in FIG. 11, the barrier 36 closely surrounds the
bottom 68, and sides 70 of the absorbent core 38 (shown in phantom)
with the liner 34 extending across and contacting the top surface
of the absorbent core 38, imparting a generally rectangular
boat-shaped configuration to the insert 32. The bottom 68 of the
barrier 36 may include one or more relaxed localized areas adjacent
the bottom 68 of the absorbent core 38 to accommodate swelling of
the core occurring during use with, for example, a hydrogel
material. The perimeter bond 40 making the liner 34 and barrier 36
coterminous substantially around the absorbent core 38 may comprise
either intermittent bonds or, preferably, a continuous autogenous,
i.e., ultrasonic or thermal, bond. The perimeter bond 40 is
preferably undulatory along the intermediate portion of the core
38, imparting a scalloped edge for greater flexibility therein.
Significantly, the absorbent structure 32 may be integrated into
the outer cover 12 in the waist attachment zones 52, 54 while the
outer cover is at least partially stretched in the cross-body
direction 41. Preferably, the longitudinal length of the free-span
zone 56 in the front 28 and rear 30 panels is at least about 2.5
inches or the longitudinal length between the waist and leg
openings.
A preferred method of integrating the absorbent insert structure 32
into the resiliently stretchable breathable outer cover 12 and
assembling the instant disposable absorbent garment 10 comprises
the steps of providing the outer cover 12 with opposed front 13 and
rear 14 waist sections, a central crotch section 16, front 28 and
rear 30 waist panels extending between the crotch and the waist
sections, prestretching the outer cover more than about 20%,
preferably from about 20% to about 200%, in the cross-body
direction 41 while superposing the insert 32 upon the outer cover,
then bonding the longitudinally opposed ends 62, 64 of the insert
to the waist sections 13, 14 in the selected waist attachment zones
52, 54, defining one or more free-span zones 56 allowing
substantially unrestricted functional stretchability of the outer
cover 12 underlying the free-span zones 56 (FIG. 10). One aspect of
the present integration method comprises the step of inwardly
folding over the outermost edges of the waist sections 13, 14
forming waist hems 66 entrapping the longitudinally opposed ends
62, 64 of the absorbent insert therein and bonding the opposed ends
62, 64 of the insert within the waist hems 66 at the waist
attachment zones 52, 54 (FIGS. 10 and 11). As disclosed above,
however, the waist opening may be elasticized by a breathable
elastomeric nonwoven laminar border strip rather than elastomeric
waist hems.
With respect to the physical properties required of the fastening
system shown in FIG. 2, it has been found that the primary closures
adjacent the leg and waist openings should have a peel strength
from about 600 grams to about 2,500 grams, depending upon the outer
cover material and the ability or strength of the parent or other
user to open the closures. The secondary closures should have a
shear strength greater than about 3,750 grams per square inch. The
full-length closures maintain the dimensional integrity of the
garments with minimal sagging of the waist or gapping and blousing
at the hips during wear. The combination of desired peel and shear
strength ranges for the fastening system shown in FIG. 2 is also
applicable to the alternative fastening system shown by FIGS. 8-16,
that is, the fastening system should have a combined peel strength
in the 600 gram to 2,500 gram range and shear strength greater than
about 3,750 grams per square inch, as determined by the measurement
methods set forth in said application Ser. No. 947,947.
FIGS. 4-7 show a disposable diaper 10 of the instant invention as
it would be worn by a baby wherein the disposable diaper has a
neat, trim, anatomically form-fitting appearance when viewed from
different perspectives. Particularly, there is shown in FIGS. 4, 5
and 7 the proper positioning of the diaper 10 on a wearer during
use, as aided by the abdominal support band 65.
Referring to FIG. 4, the elasticized waist sections 13, 14 define a
waist opening providing, at least in part a fit line W which
corresponds to the lower umbilical region of a wearer, for optimal
anatomical conformity and aesthetic appearance of the garment 10
when securely worn. Spaced from the waist sections 13, 14, the
abdominal support band 65 extends angularly downwardly relative to
said front waist section 13 defining, at least in part, a natural
abdominal support line corresponding generally to a line extending
anteriorly about the body from the dorsal side of the
transtubercular plane over the iliac crests and across the
abdominal hypogastric region of a wearer.
FIG. 7 illustrates the self-adjusting functionality of the diaper
aided by the abdominal support band 65, as shown by the minimal
extent the diaper moves or sags from an initial position as
indicated by the dashed lines 18'and 13'after being worn by an
infant for a period of time.
Although the abdominal support band 65 discussed above in
conjunction with Figures 1, 2 and 4-7 does provide a natural
support line corresponding to the lower abdominal region of the
wearer, the support band 65 provides only a limited degree of
distribution of the tensile stresses across the front waist panel
when the diaper is worn. During wear, it is desirable to direct
tensile stresses away from those portions of the leg and waist
openings that typically experience red marking. The placement and
positioning of a fastening system which is nonstretchable can
reduce forces near the leg opening and direct forces across the
outer cover to support the absorbent, especially when wet,
resulting in reduced diaper sag and droop, as will be shown herein
in conjunction with FIGS. 8-16.
Referring to FIG. 8, there is depicted a disposable diaper 10
having the absorbent structure 32 attached and integrated within
the elastomeric nonwoven outer cover 12. The front 28 and rear 30
waist panels are resiliently stretchable in the cross-body
direction 41 and are engageable with one another to define a waist
opening along the uppermost edges of the waist sections 13, 14. The
sides 15 extend between and interconnect the waist sections,
delimiting the pair of leg openings 18. The leg openings 18 may be
either elastically contractible to gather the garment about the
legs of a wearer or may be expansible, depending upon the
particular fit parameters desired. The rear pair of ears 20, 22
define elongated shapes presenting inner, body-facing surfaces
superposable on externally-facing surfaces 74 of the front pair of
ears 24, 26, as shown in FIG. 8. A pair of inelastic landing zones,
generally indicated at 70, are appointed within given areas (shown
by the phantom lines 72 in FIG. 8A, 10 and 11) of the external
surfaces 74 of the front pair of ears. The landing zones 70 have
fastening means, generally indicated at 76, provided thereon which
are releasably engageable with fastening means, also indicated at
76, provided on the inner surfaces 78 of the rear pair of ears, as
shown in FIG. 11. The landing zones 70 are selectively shaped,
sized and oriented on the external surfaces 74 of the front ears so
as to impart a tensile force distribution pattern directing
stresses away from the leg 18 and waist openings defined by the
waist sections 13, 14, while providing a band of abdominal support
across the front waist panel 28 when the garment is securely
fastened about a wearer, as will be appreciated with reference to
the discussion herein.
Referring again to FIG. 8, the landing zones 70 may be shaped in a
generally rounded or angular polygonal area. The width of the
polygon (FIGS. 8 and 8A) narrows preferably, tapering in order to
gradually concentrate forces away from the waist opening and the
leg openings. The placement and positioning of the fastener landing
zones 70, which are nonstretchable, define areas in a stretchable
diaper, such as the front waist panel 28, which define regions of
higher tensile forces therebetween, depending on the distances
between points on the landing zones 70 and the stress/strain
properties of the materials used for the outer cover 12. In this
manner, tensile forces in the diaper can be directed to desired
regions. Fastener position can, therefore, reduce forces near the
leg openings and/or direct forces in the outer cover across an
absorbent pad held therein to reduce diaper sag and droop. This is
because a nonstretchable component bonded to a stretchable material
eliminates stretch in the bonded region. When a fastener is bonded
to a stretchable outer cover such as in the instant invention, the
fastener shape generates zones where the outer cover must stretch
to a greater extent and thus is at higher tension as defined by its
stress/strain curve. Referring to FIG. 12A, triangularly shaped
landing zones 70 direct forces across the front panel 28 to
increase tension at the hips generally along the line A. The
tension generated between the landing zones is proportional to the
distance between fixed points on the landing zones, for example,
the tension generated between end points of the segment A is
greater than that generated along the line B, which is, in turn,
greater than that generated along the line C. Such a landing zone
placement operates to increase tension in the hip regions of the
front panel 28. In similar fashion, the landing zone placement may
be selected to increase tension at the waist opening, as shown in
FIG. 12B wherein tension is greatest generally along the line A,
with lines B and C representing lessening tensions approaching the
leg openings 18. To increase tension in a localized region, it is
necessary, as discussed above, to define a given area which
represents a nonstretchable zone. This may be accomplished with
either a bonded piece of material, or simply a bond pattern, as
shown in FIG. 8A, wherein the given area 72 is surrounded by a
series of autogenous, for example, ultrasonic bonds 80 conforming
to the shape of the given area 72 and thereby defining the landing
zones 70. The fastener landing zones 70 shown in FIGS. 8, 8A and
12C direct tensile forces away from both the leg and waist openings
by providing the landing zones 70 with generally triangular shapes
which direct forces along a central line A bisecting the landing
zones, wherein the tensile forces generated along the line A are
greater than those generated between the landing zones along the
lines B (FIG. 12C).
Where the landing zone is delimited by a closed pattern of
ultrasonic bonds 80, as shown in FIG. 8A, the hook component 82 of
the fastening means 76 may be attached in a strip as shown and need
not cover the entire landing zone 70, allowing smaller amounts of
costly fastener material to be used; however, as shown in FIGS. 8
and 11, the landing zones 70 could comprise entire pieces of
fastener material. The fastening means provided on the landing
zones 70 and on the inner surfaces 78 of the rear pair of ears 20,
22, preferably comprises hook and loop fastening tapes of the type
which are well known in the art and available from companies such
as, for example, Velcro, U.S.A., Inc. Nevertheless, it will be
appreciated by those skilled in the art that other forms of
mechanical or even adhesive fastening means could be used in the
diaper of the present invention. Preferably, where hook and loop
fasteners are used, the loop portion 82 should be located on the
inner, body-facing surfaces 78 of the rear pair of ears 20, 22 and
the harsher hook portions 84 should be located on the landing zones
70, as shown in FIG. 11 to minimize potential skin contact
therewith. It is preferable to further isolate the harsh hook
portions 84 from possible contact with the skin of a wearer's leg
by forming flaps 86 which cover a lower marginal portion of the
hook material. The flaps 86 may be formed by outwardly folding over
marginal edges of the leg openings 18 adjacent the front waist
panel 28, as shown in FIG. 8.
Alternatively, the front ears may be further elongated in a
cross-body direction and the landing zones tapered and elongated so
that their width narrows distally in a direction away from the
centerline, thereby enabling the fastening means to be secured
together along substantially the full tapered length of the landing
zones to provide a longer closure along the sides of the garment,
where desired, between the front and rear waist panels from the leg
openings to the waist openings, while avoiding fastener-skin
contact (not shown).
Referring to FIGS. 9A, 9B and 12C, there is shown an alternative to
the fastening system constructed in accordance with the present
invention. Not only is it possible to minimize the amount of
material used for the hook component 84 used as a mechanical
fastening element on the landing zone 70 (FIG. 8A), but it is also
possible to minimize the amount of loop material 82 utilized on the
body-facing surfaces 78 of the rear pair of ears, of which a
representative ear 22 is illustratively shown. With further
reference to FIGS. 9A and 9B, there is shown an adjustable
combination fastening system wherein the rear pair of elongated
ears 22 comprise proximal portions 88 equidistantly spaced from the
centerline, user end portions 90 spaced distally from the proximal
portions 88 and elastomeric medial portions 92 adjustably spacing
the user portions 90 from the proximal portions 88. The hook
component 84 of the mechanical fastening means 76 is provided on
the landing zones 70 appointed on the externally-facing surfaces 78
of the front ears 24, 26, of which a single front ear 26 is
illustratively shown in FIGS. 9A and 9B. Fixed-position mechanical
fastening means, such as the snaps generally indicated at 94, are
provided on the external surface 74 of the front ear 26 and the
bodyside surface 78 of the rear ear 22. The hook 84 and loop 82
components on the landing zones 70 and the proximal portion 88 of
the rear ear 22, respectively, comprise variable-position
mechanical fastening means which are initially engaged when
fastening the diaper garment 10, as shown in FIG. 9B. Once the
strip of loop component 82 is engaged at a desired location with
the hook component 84 on the landing zones 70, the user end 90
bearing the snap element 94 may be stretched to cover the remainder
of the hook component 84, as shown by the sequential arrows 96
(FIG. 9B) and 98 (FIG. 9A) sufficiently to allow the mating snap
elements 94 to be engaged with one another. In this manner, the
medial portion 92 of the rear ear imparts a certain degree of
adjustability to the mechanical fastening means, while providing a
secure fixed snap engagement which is more resistant to tampering
by a child. FIG. 12C illustrates the placement of the
fixed-position fastening means 94 with respect to the landing zones
70. In this arrangement, the fixed-point fastening means 94 are
functionally a part of the landing zones 70 and define a shortest
distance A therebetween wherein the tensile forces in the front
waist panel 28 concentrate and are of the greatest magnitude
relative to the tensile forces elsewhere between the landing zones,
as represented by the distances B in FIG. 12C.
FIGS. 10 and 1OA show an internal perspective view of the assembled
garment having the preferred fastening arrangement of the present
invention. Other nonfastening structures are indicated which are
similar to those discussed in conjunction with FIG. 2.
A preferred method for making the landing zones of the present
invention is further illustrated by reference to the exploded
perspective view of the garment shown in FIG. 11. The method
comprises the steps of providing an absorbent structure 32 adapted
for absorbing and containing body wastes and providing an
elastomeric nonwoven outer cover 12 adapted for holding the
absorbent structure 32 in a selected bodily registration when the
garment 10 is securely worn. The outer cover 12 is provided with
front 28 and rear 30 waist panels resiliently stretchable in a
cross-body direction 41 and an intermediate crotch panel 16
separates the waist panels 28, 30 from one another, with a pair of
sides 15 extending between and interconnecting the waist panels.
Delimited along the sides 15 are a pair of leg openings 16 which
may be elastically contractible by means of the supplemental
gathers 58 or may be sized so that elastic expansibility is relied
upon for appropriate leg fit. Fastening means, specifically the
soft loop component 82, are provided on the internally-facing
surfaces 78 of the rear pair of ears 20, 22. Inelastic landing
zones 70 are appointed on given areas 72 of external surfaces 74 of
the front pair of ears 24, 26, with hook components 84 of the
fastening means provided on the landing zones 70, which are formed
with a selected shape and size. The landing zones 70 are then
oriented and bonded, such as with the autogenous bonds 80 shown in
FIG. 8A, onto the given areas 72 of the external surfaces 74.
Also with reference to FIGS. 13-16, the subject fastening system is
integrated into the diaper design to function cooperatively with
the other components of the diaper 10 and requires similar familiar
hand motions as conventional tape systems, taking the same time to
fasten. It also utilizes materials with which users are comfortable
and familiar, that is, snaps and hook and loop fasteners. The
subject diaper fastening system stays fastened, is refastenable, is
contamination-free, contributes to the fit characteristics of the
diaper and does not leave tell-tale red marks on the skin of a
wearer. Moreover, the subject fasteners rely more on the inherent
stretch characteristics of the outer cover by increasing the outer
cover tension across the front waist panel 28. They also more
conveniently place the fastener target on the front panel 28 of the
diaper 10 and offer an easy one-step closure. The elongated ears
20, 22 are easily handled and apparent tightness of the garment is
reduced while offering a gentler waist and leg fit. The instant
invention reduces droop and holds the absorbent structure in a
desirable position against the wearer as seen in FIGS. 13, 14, 15
and, particularly in FIG. 16.
Turning now to the outer cover 12 of the present invention, which
is preferably made from a resiliently stretchable elastomeric
nonwoven laminar material having a stretchability of from about 20
percent to about 200 percent. The term stretchability as used
herein is defined by the following relationship:
Since the outer cover 20 is also resilient, the outer cover returns
essentially to its initial dimension when the stretching force is
removed.
One such resiliently stretchable material is disclosed in U.S. Pat.
No. 4,663,220 to Tony J. Wisneski and Michael T. Morman, assigned
to the assignee of the present application, entitled
"Polyolefin-containing Extrudable Compositions and Methods for
their Formation Into Elastomeric Products", the entire disclosure
of which is incorporated herein by reference and relied upon. That
patent provides extrudable elastomeric compositions which, after
extrusion, solidify to form elastomeric products such as, for
example, fibrous nonwoven elastomeric webs. The extrudable
elastomeric compositions are blends of (1) from at least about 10
percent, by weight, of an A-B-A' block copolymer, where "A" and
"A'" are each a thermoplastic polymer endblock which includes a
styrenic moiety such as a poly(vinyl arene) and where "B" is an
elastomeric poly(ethylene-butylene) midblock, with (2) from greater
than 0 percent, by weight, to about 90 percent, by weight, of a
polyolefin which, when blended with the A-B-A' block copolymer and
subjected to appropriate elevated pressure and elevated temperature
conditions, is extrudable, in blended form, with the A-B-A' block
copolymer. The A-B-A' block copolymer serves to impart elastomeric
properties to products formed from the extrudable composition and
the presence of the polyolefin in the blend serves to reduce the
viscosity of the composition as compared to the viscosity of the
neat, that is, pure, A-B-A' block copolymer and thus enhances the
extrudability of the composition.
Preferably, the "A" and "A'" thermoplastic styrenic moiety
containing endblocks of the block copolymer are selected from the
group including polystyrene and polystyrene homologs such as, for
example, poly(alpha-methylstyrene). In some embodiments the "A"and
"A'" thermoplastic styrenic moiety containing endblocks are
identical. Preferably, the polyolefin is selected from the group
including at least one polymer selected from the group including
polyethylene, polypropylene, polybutene, ethylene copolymers,
propylene copolymers, butene copolymers or blends of two or more of
these materials.
The blend usually includes from at least about 20 percent, by
weight, to about 95 percent, by weight, of the block copolymer and
from at least about 5 percent, by weight, to about 80 percent, by
weight, of the polyolefin. For example, the blend may include from
about 30 percent, by weight, to about 90 percent, by weight, of the
block copolymer and from about 10 percent, by weight, to about 70
percent, by weight, of the polyolefin. Preferably, the blend
includes from about 50 percent, by weight, to about 90 percent, by
weight, of the block copolymer and from about 10 percent, by
weight, to about 50 percent, by weight, of the polyolefin. For
example, the blend may include from about 50 percent, by weight, to
about 70 percent, by weight, of the block copolymer and from about
30 percent, by weight, to about 50 percent, by weight, of the
polyolefin. One blend includes about 60 percent, by weight, of the
polyolefin.
The extrudable composition is extruded or otherwise formed, such
as, for example, by molding, for example, injection molding, at an
appropriate, that is effective, combination of elevated pressure
and elevated temperature conditions. These conditions will vary
depending on the polyolefin utilized. For example, the extrudable
composition should be extruded or otherwise formed at a temperature
of at least about 125 degrees Centigrade if polyethylene is
utilized as the polyolefin in the blend or at least about 175
degrees Centigrade if polypropylene is utilized in the blend, for
example, at a temperature of from at least about 290 degrees
Centigrade to about 345 degrees Centigrade, more specifically, at a
temperature of from at least about 300 degrees Centigrade to about
335 degrees Centigrade, into elastomeric products such as, for
example, elastomeric fibers, which may be collected as a fibrous
nonwoven elastomeric web.
Preferably the blends are extrudable within the above-defined
temperature ranges at elevated pressures within the die tip, (for
example, within the extrusion capillaries of a die tip having
thirty (30 ) extrusion capillaries per lineal inch of die tip with
each of the capillaries having a diameter of 0.0145 inches and a
length of 0.113 inches) of no more than about 300 pounds per square
inch, gage, for example, from pressures of from about 20 pounds per
square inch, gage, to about 250 pounds per square inch, gage. More
specifically, the blends are extrudable within the above-defined
temperature ranges at pressures of from about 50 pounds per square
inch, gage, to about 250 pounds per square inch, gage, for example,
from about 125 pounds per square inch, gage, to about 225 pounds
per square inch, gage. Higher elevated pressures can be utilized
with other die designs having a lower number of capillaries per
inch of die, but, generally speaking, lower production rates
result.
Importantly, it has been found that the extrudable compositions are
extrudable at satisfactory throughput rates because the presence of
the polyolefin in the extrudable composition reduces the viscosity
of the extrudable composition, as compared to the viscosity of the
neat, that is, pure, block copolymer, to satisfactory levels. This
reduced viscosity proportionally reduces the die tip pressure if
all other parameters remain the same. For example, the viscosity of
the extrudable compositions will generally be less than about 500
poise when extruded at the above-defined elevated temperature and
elevated pressure ranges. Preferably, the viscosity of the
extrudable composition is less than about 300 poise when extruded
at the above-defined elevated temperatures and elevated pressure
ranges. For example, the viscosity of the extrudable composition
may be from at least about 100 poise to about 200 poise when
extruded at the above-identified elevated temperature and elevated
pressure conditions.
Because the polyolefin reduces the viscosity of the blend, as
compared to the viscosity of the block copolymer, the extrudable
composition is extrudable within the above-identified elevated
temperature and elevated pressure ranges, through a die tip having,
for example, thirty capillaries per inch of die tip with the
capillaries having a diameter of about 0.0145 inches and a length
of about 0.113 inches at a rate of from at least about 0.02 grams
per capillary per minute to about 1.7 or more grams per capillary
per minute. For example, the extrudable composition may be extruded
through the above-identified die tip having capillaries with a
diameter of about 0.0145 inches and a length of about 0.113 inches
at the rate of from at least about 0.1 grams per capillary per
minute to about 1.25 grams per capillary per minute. Preferably,
the extrudable composition is extrudable through the
above-identified die tip having capillaries with a diameter of
about 0.0145 inches and a length of about 0.113 inches at the rate
of from at least about 0.3 grams per capillary per minute to about
1.7 grams per capillary per minute.
The extrudable composition may be formed into fibrous nonwoven
elastomeric webs preferably having microfibers with an average
diameter of not greater than about 100 microns, and preferably
having an average basis weight of not more than about 300 grams per
square meter, for example, an average basis weight of from about 5
grams per square meter to about 100 grams or more per square meter.
More specifically, an average basis weight of from about 10 grams
per square meter to about 75 grams per square meter. For example, a
fibrous nonwoven elastomeric web may be formed by extruding the
extrudable composition at an appropriate, that is, effective,
combination of elevated temperature and elevated pressure
conditions. Preferably, the extrudable composition is extruded at a
temperature of from at least about 125 degrees Centigrade if the
polyolefin is polyethylene or at least about 175 degrees Centigrade
if the polyolefin is polypropylene, for example, from about 290
degrees Centigrade to about 345 degrees Centigrade, more
specifically from about 300 degrees Centigrade to about 335 degrees
Centigrade. Preferably, the extrudable composition is extruded
within the above-identified temperature ranges and pressures,
within the die tip, (for example, within the extrusion capillaries
of a die tip having thirty (30 ) extrusion capillaries per lineal
inch of die tip with each of the capillaries having a diameter of
about 0.0145 inches and a length of 0.113 inches) of no more than
about 300 pounds per square inch, gage, for example, from about 20
pounds per square inch, gage, to about 250 pounds per square inch,
gage. More specifically, the extrudable composition is extruded at
a pressure within the capillaries of the above-identified die tip
of from about 50 pounds per square inch, gage, to about 250 pounds
per square inch, gage, for example, from about 125 pounds per
square inch, gage, to about 225 pounds per square inch, gage.
In the formation of elastomeric nonwoven webs, the extrudable
composition is extruded, at the above-defined elevated temperature
and elevated pressure conditions at a rate of from at least about
0.02 gram per capillary per minute to about 1.7 or more grams per
capillary per minute, for example, from at least about 0.1 gram per
capillary per minute to about 1.25 grams per capillary per minute,
more specifically, from at least about 0.3 gram per capillary per
minute to about 1.1 grams per capillary per minute, through a die
having a plurality of small diameter extrusion capillaries, as
molten threads into a gas stream which attenuates the molten
threads to provide a gas-borne stream of microfibers which are then
formed into the fibrous nonwoven elastomeric web upon their
deposition on a collecting arrangement. The attenuating gas stream
is applied to the molten threads at a temperature of from at least
about 100 degrees Centigrade to about 400 degrees Centigrade, for
example, from about 200 degrees Centigrade to about 350 degrees
Centigrade and at a pressure of from at least about 0.5 pound per
square inch, gage, to about 20 pounds per square inch, gage, for
example, from at least about 1 pound per square inch, gage, to
about 10 pounds per square inch, gage. The thread attenuating gas
stream may be an inert, non-oxidizing, gas stream such as, for
example, a stream of nitrogen gas. In some embodiments the velocity
and temperature of the thread-attenuating gas stream is adjusted so
that the fibers are collected as substantially continuous fibers
having diameters of from about ten (10) microns to about sixty (60
) microns, for example, from at least about ten (10) microns to
about forty (40) microns. The fibrous nonwoven elastomeric webs so
formed will include elastomeric fibers composed of from at least
about 10 percent, by weight, of the block copolymer and greater
than 0 percent, by weight, and up to about 90 percent, by weight,
of the polyolefin. The fibers are usually composed from at least
about 20 percent, by weight, to about 95 percent, by weight, of the
block copolymer and from at least about 5 percent, by weight, to
about 80 percent, by weight of the polyolefin. For example, the
fibers may be composed from at least about 30 percent, by weight,
to about 90 percent, by weight, of the block copolymer and from at
least about 10 percent, by weight, to about 70 percent, by weight,
of the polyolefin. Preferably, the fibers are composed from about
50 percent, by weight, to about 90 percent, by weight, of the block
copolymer and from at least about 10 percent, by weight, to about
50 percent, by weight, of the polyolefin. For example, the fibers
may be composed from at least about 50 percent, by weight, to about
70 percent, by weight, of the block copolymer and from at least
about 30 percent, by weight, to about 50 percent, by weight, of the
polyolefin.
Another such resiliently stretchable material is disclosed in U.S.
Pat. application, Ser. No. 760,437 in the name of Jack D. Taylor
and Michael J. Vander Wielen and assigned to the assignee of the
present application, entitled "Composite Elastomeric Material and
Process for Making the Same", the entire disclosure of which is
incorporated herein by reference and relied upon. That application
provides a method of producing a composite elastic material
comprising at least one gatherable web bonded to at least one
elastic web, the method comprising (a) tensioning an elastic web
(which may comprise a fibrous web such as a nonwoven web of
elastomeric fibers, for example, meltblown elastomeric fibers) to
elongate it; (b) bonding the elongated elastic web to at least one
gatherable web under conditions which soften at least portions of
the elastic web to form a bonded composite web; and (c) relaxing
the composite web immediately after the bonding step whereby the
gatherable web is gathered to form the composite elastic material.
The fibrous elastic web can also be maintained in a stretched
condition during the bonding, at an elongation of at least about 25
percent, preferably about 25 percent to over 500 percent, for
example, about 25 percent to 550 percent elongation during the
bonding. The method also includes bonding the elongated elastic web
to the gatherable web by overlaying the elastic and gatherable webs
and applying heat and pressure to the overlaid webs, for example,
by heating bonding sites on the elastic web to a temperature of
from at least about 65 degrees Centigrade to about 120 degrees
Centigrade, preferably from at least about 70 degrees Centigrade to
about 90 degrees Centigrade.
That application also provides an elastic composite material
comprising an elastic web bonded to at least one gatherable web
which is extensible and contractible with the elastic web upon
stretching and relaxing of the composite material, the elastic
composite material being made by a method as described above. Also
provided is an elastic web that is bonded to the gatherable web at
a plurality of spaced-apart locations in a repeating pattern and
the gatherable web is gathered between the bonded locations. The
elastic web may comprise a nonwoven web of elastomeric fibers,
preferably elastomeric microfibers, such as, for example, an
elastomeric nonwoven web of meltblown elastomeric fibers or an
elastomeric film.
The elastic composite material may include one or more of the
following in any combination: the elastomeric fibers, preferably
meltblown elastomeric fibers, may be formed from material selected
from the group including (i) A-B-A' block copolymers wherein "A"
and "A'" may be the same or different endblocks and each is a
thermoplastic polymer endblock or segment which contains a styrenic
moiety such as polystyrene or polystyrene homologs, and "B" is an
elastomeric polymer midblock or segment, for example, a midblock
selected from the group including poly(ethylene-butylene),
polyisoprene and polybutadiene, with poly(ethylene-butylene) being
preferred and (ii) blends of one or more polyolefins with the
A-B-A' block copolymers of (i) where "B" is a
poly(ethylene-butylene) midblock; each of the "A" and "A'"
endblocks may be selected from the group consisting of polystyrene
and polystyrene homologs, for example, poly(alpha methylstyrene),
and where the elastomeric fibers are formed from a blend of one or
more polyolefins with an A-B-A' block copolymer where "B" is a
poly(ethylene-butylene) midblock, the polyolefin is selected from
one or more of polyethylene, polypropylene, polybutene, ethylene
copolymers, propylene copolymers and butene copolymers; the
elastomeric film and the elastomeric fibers which form the
elastomeric nonwoven web, for example, the meltblown microfibers,
are composed of at least 10 percent, for example at least 20
percent, more specifically at least 30 percent, for example, from
about 10 percent to 90 percent, by weight, of the aforesaid A-B-A'
block copolymers and greater than 0 percent, by weight, for
example, from about 90 percent to about 10 percent, by weight, of
the polyolefin; the elastic web, for example, a fibrous elastic
web, is bonded to the gatherable web at a plurality of spaced-apart
locations in a repeating pattern and the gatherable web is gathered
between the bonded locations; the elastic web preferably has a low
basis weight of from about 5 to about 300, preferably from about 5
to about 200, grams per square meter, for example, from about 5 to
about 100 grams per square meter, although its basis weight can be
much higher; the gatherable web is a nonwoven, non-elastic
material, preferably one composed of fibers formed from materials
selected from the group including polyester fibers, for example,
poly(ethylene terephthalate) fibers, polyolefin fibers, polyamide
fibers, for example, nylon fibers, cellulosic fibers, for example,
cotton fibers, and mixtures thereof. Alternatively, the gatherable
web may be any suitable woven fabric. In a particular aspect, the
composition of the A-B-A' polymer used is such that the sum of the
molecular weight of "A" with the molecular weight of "A'" is from
about 14 to 31percent (from about 14 to 29 percent when "B" is
poly(ethylene-butylene)) of the molecular weight of the A-B-A'
block copolymer.
A further such resiliently stretchable material is disclosed in
U.S. Pat. No. 4,657,802 to Michael J. Morman, assigned to the
assignee of the present invention and entitled "Composite Nonwoven
Elastic Web" , the entire disclosure of which is incorporated
herein by reference and relied upon. That patent is directed to a
process for producing a composite nonwoven elastic web which is
composed of a nonwoven elastic web that is joined to a fibrous
nonwoven gathered web. In particular, the process disclosed therein
produces a composite nonwoven elastic web which, in its relaxed,
nonstretched state, is composed of a gathered nonwoven fibrous web
that is joined to a nonwoven elastic web with the nonwoven elastic
web having been relaxed from a stretched, biased length to a
relaxed, unbiased, nonstretched length so as to gather the fibrous
nonwoven gathered web. An important feature of the process
disclosed therein is that the fibrous nonwoven gatherable web is
formed directly onto a surface of the nonwoven elastic web while
the nonwoven elastic web is maintained in a stretched, biased and
elongated condition. The nonwoven elastic web may be formed by, for
example, a meltblowing process or any other process for forming a
nonwoven elastic web. For example, the nonwoven elastic web could
be an apertured web of an elastic film as opposed to a meltblown
fibrous nonwoven elastic web. The formed nonwoven elastic web has a
normal relaxed, nonstretched, nonbiased length. Thereafter, the
nonwoven elastic web is elongated by being stretched to a
stretched, biased length. In a subsequent step of the process a
fibrous nonwoven gatherable web may be formed, for example, by
either a meltblowing or spunbonding process or any other process
for forming a fibrous nonwoven gatherable web, directly upon a
surface of the nonwoven elastic web while the nonwoven elastic web
is maintained at its elongated, stretched and biased length. During
formation of the fibrous nonwoven gatherable web the nonwoven
elastic web is maintained at a stretched length which is at least
about 125percent, that is, at least about one and one quarter of
the relaxed, unbiased length of the nonwoven elastic web. For
example, the stretched, biased length of the nonwoven elastic web
may be maintained in the range of from at least about 125 percent
of the relaxed, unbiased length of the nonwoven elastic web to
about 700 or more percent of the relaxed, unbiased length of the
nonwoven elastic web. The fibrous nonwoven gatherable web is joined
to the nonwoven elastic web while the nonwoven elastic web is
maintained at its elongated stretched, biased length. This results
in the formation of a composite nonwoven elastic web which includes
the nonwoven elastic web which is joined to the fibrous nonwoven
gatherable web. Because the fibrous nonwoven gatherable web is
formed directly onto the surface of the nonwoven elastic web while
the nonwoven elastic web is being maintained at its stretched,
biased length, the nonwoven elastic web is, at this stage in the
process, elongated, stretched and biased and the fibrous nonwoven
gatherable web is in an ungathered but gatherable condition. In one
aspect, the joining of the fibrous nonwoven gatherable web to the
nonwoven elastic web is achieved by heat-bonding to fuse the two
webs to each other. The heat-bonding may be carried out within the
temperature range of from about 50 degrees centigrade below the
melt temperature of at least one of the materials utilized to form
at least one of the two webs to about the melt temperature of at
least one of the materials utilized to form at least one of the two
webs. At high through-put rates the heat-bonding can be carried out
above the melt temperature of one or more of the materials utilized
to form the webs. The heat-bonding may also be carried out under
appropriate conventional pressurized conditions. If desired,
conventional sonic bonding techniques may be substituted for the
heat-bonding steps.
The patent also discloses another embodiment whereby the joining of
the fibrous nonwoven gatherable web to the stretched nonwoven
elastic web is achieved solely by the entanglement of the
individual fibers of the fibrous nonwoven gatherable web with the
nonwoven elastic web during formation of the fibrous gatherable web
on the surface of the elastic web. If the nonwoven elastic web is a
fibrous nonwoven elastic web formed by, for example, meltblowing,
entanglement of the individual fibers of the fibrous nonwoven
gatherable web with the fibrous nonwoven elastic web is achieved by
entanglement of the individual fibers of the fibrous gatherable web
with the individual fibers of the fibrous elastic web. If the
nonwoven elastic web is an apertured film, joining of the fibrous
nonwoven web with the film is achieved by entanglement of the
individual fibers of the fibrous gatherable web within the
apertures of the film. The joining of the two webs to each other
can also be achieved by forming the nonwoven elastic web out of a
tacky elastic material, a process that will be discussed
hereinafter. In addition, the joining of the two webs to each other
may be further enhanced by applying pressure to the two webs after
the gatherable web has been formed on the surface of the elastic
web. Further improvement in the joining of the two webs can be
obtained by applying an adhesive material to the upper surface of
the nonwoven elastic web prior to formation of the fibrous nonwoven
gatherable web thereon.
After joining of the two webs to each other has been achieved to
form a composite elastic web, the biasing force is removed from the
composite nonwoven elastic web and the composite elastic web is
allowed to relax to its normal relaxed, unbiased length. Because
the fibrous nonwoven gatherable web is joined to the nonwoven
elastic web while the nonwoven elastic web is stretched, relaxation
of the composite nonwoven elastic web results in the gatherable web
being carried with the contracting nonwoven elastic web and thus
being gathered. After gathering of the fibrous nonwoven gatherable
web has occurred by reducing the biasing force on the composite
nonwoven elastic web, the composite nonwoven elastic web may be
rolled up in rolls for storage and shipment of directed to a
manufacturing process for the production of products such as the
disposable garments taught by the present application.
As indicated above, the process disclosed in U.S. Pat. No.
4,657,802 can be enhanced by the utilization of a tacky fibrous
nonwoven elastic web which can be formed by, for example,
meltblowing microfibers of a tacky elastic material such as, for
example, an A-B-A' block copolymer or blends of such A-B-A' block
copolymers with poly(alpha-methylstyrene) where "A" and "A'" are
each thermoplastic polystyrene or polystyrene homolog endblocks and
"B" is an elastic polyisoprene midblock. In some embodiments "A"
may be the same thermoplastic polystyrene or polystyrene homolog
endblock as "A'". The tacky fibrous nonwoven elastic web is then
elongated by being stretched to an elongated, stretched length and
a fibrous nonwoven gatherable web is formed, for example, by
meltblowing or spunbonding the fibrous nonwoven gatherable web,
directly upon a surface of the tacky fibrous nonwoven elastic web
while maintaining the fibrous nonwoven elastic web at its stretched
length. As a result of the fact that the fibrous nonwoven elastic
web is tacky, the fibrous nonwoven gatherable web is simultaneously
formed upon and adhesively joined to the surface of the tacky
fibrous nonwoven elastic web. This results in the formation of a
composite nonwoven elastic web having an ungathered fibrous
gatherable web adhesively joined to the tacky fibrous nonwoven
elastic web with the joining of the two webs to each other being
achieved by the adhesive joining which occurs during formation of
the fibrous nonwoven gatherable web on the surface of the fibrous
nonwoven elastic web. The adhesive joining of the two webs to each
other may be increased upon application of pressure to the
composite nonwoven elastic web by passing the composite nonwoven
elastic web through the nip between rollers, which may be unheated,
after the composite web has been formed but before the fibrous
tacky nonwoven elastic web is allowed to relax. The adhesive
joining may be further enhanced by application of an adhesive
material to the surface of the tacky fibrous nonwoven elastic web
prior to formation of the gatherable web thereon. The composite
nonwoven elastic web is then allowed to relax to its normal
relaxed, unbiased length. Because the fibrous nonwoven gatherable
web is joined to the tacky fibrous nonwoven elastic web while the
tacky fibrous nonwoven elastic web is in a stretched condition,
relaxation of the composite nonwoven elastic web and thus the tacky
fibrous nonwoven elastic web results in the gatherable web being
carried with the contracting fibrous nonwoven elastic web and thus
being gathered. After gathering of the fibrous nonwoven gatherable
web has occurred the composite nonwoven elastic web may be rolled
up in rolls for storage or directly applied to a manufacturing
process for the production of disposable garments such as the
disposable garments taught by the present application.
The U.S. Pat. No. 4,657,802 is also directed to a composite
nonwoven elastic web composed of a nonwoven elastic web that is
joined to a gatherable fibrous nonwoven web which has been gathered
and with the composite web having been formed by any of the
embodiments of the process disclosed above. In particular, the
composite nonwoven elastic web, in its relaxed, nonstretched state,
is composed of a nonwoven elastic web that is joined to a fibrous
nonwoven gathered web which has been gathered as a result of the
nonwoven elastic web having been relaxed from an elongated
stretched, biased length to a relaxed, unbiased nonstretched
length. Exemplary elastomeric materials for use in formation of the
fibrous nonwoven elastic web include polyester elastomeric
materials, polyurethane elastomeric materials, and polyamide
elastomeric materials. Other elastomeric materials for use in
formation of the fibrous nonwoven elastic web include (a) A-B-A'
block copolymers, where "A" and "A'" are each a thermoplastic
polymer endblock which includes a styrenic moiety and where "A"may
be the same thermoplastic polymer endblock as "A'", such as a
poly(vinyl arene), and where "B" is an elastomeric polymer midblock
such as a conjugated diene or a lower alkene or (b) blends of one
or more polyolefins or poly(alpha-methyl styrene) with A-B-A' block
copolymers, where "A" and " A'" are each a thermoplastic polymer
endblock which includes a styrenic moiety, where "A" may be the
same thermoplastic polymer endblock as "A'", such as a poly(vinyl
arene) and where "B" is an elastomeric polymer midblock such as a
conjugated diene or a lower alkene. The "A" and "A'" endblocks may
be selected from the group including polystyrene and polystyrene
homologs and the "B" midblock may be selected from the group
including polyisoprene, polybutadiene or poly(ethylene-butylene).
If "A" and "A'" are selected from the group including polystyrene
or polystyrene homologs and "B" is poly(ethylene-butylene),
materials which may be blended with these block copolymers are
polymers, including copolymers of ethylene, propylene, butene,
other lower alkenes or one or more of these materials. If "A" and
"A'" are selected from the group including polystyrene or
polystyrene homologs and "B" is a polyisoprene midblock, a material
for blending with this type of block copolymer is
poly(alpha-methylstyrene).
U.S. Pat. application Ser. No. 919,901, in the name of J. S.
Kieffer and Tony J. Wisneski, assigned to the assignee of the
present application, entitled "Extrudable Composition for Forming
Nonwoven Web or Pressure-Sensitive Elastomer Adhesive, and Use of
Such Extrudable Composition in Forming Nonwoven Webs and
Stretch-Bonded Laminates," the entire disclosure which is
incorporated herein by reference and relied upon, discloses another
such resiliently stretchable material. In this application, there
is disclosed an extrudable composition for forming nonwoven
elastomeric material having pressure-sensitive adhesive properties,
nonwoven elastomeric sheet material, for example, fibrous nonwoven
webs, formed of such composition, stretch-bonded laminates using
such sheets and methods of forming such sheets in such laminates.
The composition includes an elastomeric polymer and a tackifying
resin, and can also include a polyolefin. The nonwoven sheet
material can be a meltblown nonwoven web and the laminate can be
formed by tensioning the elastomeric sheet material and bonding a
gatherable web, for example, a spunbonded polypropylene web, to the
tensioned sheet material by application of pressure, the bonding
being accomplished due to the adhesivity of the elastomeric sheet
material and without application of heat for softening the sheet
material and/or gatherable web. The increased tackiness imparted to
the elastomeric sheet by this internal tackifying agent resists in
a composite web which resists delamination.
As used in the U.S. Pat. No. 4,657,802,and as contemplated herein,
the term "nonwoven web" or "nonwoven layer" includes any web of
material which has been formed without use of textile weaving
processes which produce a structure of individual fibers which are
interwoven in an identifiable repeating manner. Specific examples
of nonwoven webs would include, without limitation, a meltblown
nonwoven web, a spunbonded nonwoven web, an apertured film, a
microporous web, elastomeric netting or a carded web of staple
fibers.
It is to be clearly understood that the descriptions of methods for
making a material suitable for outer cover 12 and the description
of materials suitable for the outer cover 12 are exemplary only and
not meant to be limiting.
The bodyside liner 34 may be airlaid, a bonded carded web, a
powder-bonded carded web or a pattern bonded, spunbonded web of
synthetic fibers such as polypropylene, polyester and the like.
Various materials are contemplated for use as the absorbent core
38, including fibrous materials, foams, particulates, etc. In
general, the most economical liquid absorbent material for use in
disposable diapers has been an absorbent fiber. The absorbent fiber
most commonly used is cellulosic fiber such as comminuted wood
pulp, commonly known in the art as "pulp fluff ," or simply
"fluff."
Comminuted wood pulp (fluff) is preferred as an absorbent fiber,
but other cellulose fibers such as cotton linters can be used. The
preferred fluff is southern pine kraft wood pulp (i.e., made
according to the sulfate process commonly known in the art) which
has been bleached, such as can be purchased from International
Paper Company. Other softwood fluffs may be purchased from
Kimberly-Clark Corporation, such as CR-54. Various hardwood fluffs
may also be blended with the softwood fluffs to form the absorbent
composite. A water-swellable hydrogel material, preferably in
particulate form, may be used in a number of various arrangements
within the absorbent composite in order to decrease the bulkiness
and enhance the capacity of the composite 38. Many such hydrogel
materials are known and available to those skilled in the art. It
should be understood that additional elements could be provided in
conjunction with those already set forth, without departing from
the contemplated scope of the present invention and the description
herein is not intended to be in any way limiting.
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